Quote:5. Delayed vaccine effect ....Due to delayed effect of the vaccine, the endpoint curves may show no effect for the initial portion of the study. If the vaccine is effective, evidence of the effect may occur later in the study. This delay in the effect may lead to an average effect that is smaller than expected and thus may require both an increase in sample size to compensate for the delay and a careful assessment of trial maturity for the primary analysis. In addition, possible violation of the proportional hazards assumption should be considered when selecting a statistical method for the primary analysis. -- https://www.fda.gov/downloads/biologicsbloodvaccines/guidancecomplianceregulatoryinformation/guidances/vaccines/ucm278673.pdf

I think that is one reason why the trial is old. Only NWBO was smart and increased percentage of required events instead of number of patients. As I repeat like a broken record, if all you do is increase patients, you simply fill the event spaces with non-responders and the trial ends too quickly. Instead you want to get a higher percent of patient events from the entire group you have. This allows a trial to capture more responders as well. That's why these trials take time, but only the final results will tell us why this trial took a particularly long time. Bears think its because researchers are trying to eek out separation, longs think it's just due to separation occurring later due to crossover. Regardless, PFS should be 100% mature, but as we saw in the Seattle conference, there might be challenges determining delayed psPD from progression. That would likely by why PFS analysis took more time as well.